223 research outputs found
B-type supergiants in the SMC: Rotational velocities and implications for evolutionary models
High-resolution spectra for 24 SMC and Galactic B-type supergiants have been
analysed to estimate the contributions of both macroturbulence and rotation to
the broadening of their metal lines. Two different methodologies are
considered, viz. goodness-of-fit comparisons between observed and theoretical
line profiles and identifying zeros in the Fourier transforms of the observed
profiles. The advantages and limitations of the two methods are briefly
discussed with the latter techniques being adopted for estimated projected
rotational velocities (\vsini) but the former being used to estimate
macroturbulent velocities. Only one SMC supergiant, SK 191, shows a significant
degree of rotational broadening (\vsini 90 \kms). For the remaining
targets, the distribution of projected rotational velocities are similar in
both our Galactic and SMC samples with larger values being found at earlier
spectral types. There is marginal evidence for the projected rotational
velocities in the SMC being higher than those in the Galactic targets but any
differences are only of the order of 5-10 \kms, whilst evolutionary models
predict differences in this effective temperature range of typically 20 to 70
\kms. The combined sample is consistent with a linear variation of projected
rotational velocity with effective temperature, which would imply rotational
velocities for supergiants of 70 \kms at an effective temperature of 28 000 K
(approximately B0 spectral type) decreasing to 32 \kms at 12 000 K (B8 spectral
type). For all targets, the macroturbulent broadening would appear to be
consistent with a Gaussian distribution (although other distributions cannot be
discounted) with an half-width varying from approximately 20 \kms
at B8 to 60 \kms at B0 spectral types.Comment: 4 figures, 8 pages, submitted to Astronomy and Astrophysic
Chemical constituents of lawang root oil
Spectroscopic analysis of lawang root oil identified methyl salicylate as the major component. This result contrasts with the known composition of bark-derived lawang oil, in which eugenol is the major component. The validity of the compositional analysis was confirmed by extraction of an authentic sample of plant root tissue, and comparison with the commercially available essential oil
Terminal velocities of luminous, early-type SMC stars
Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are
used to determine terminal velocities for 11 O and B-type giants and
supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV
resonance lines. Using archival data from observations with the Goddard
High-Resolution Spectrograph and the International Ultraviolet Explorer
telescope, terminal velocities are obtained for a further five B-type
supergiants. We discuss the metallicity dependence of stellar terminal
velocities, finding no evidence for a significant scaling between Galactic and
SMC metallicities for Teff < 30,000 K, consistent with the predictions of
radiation driven wind theory for supergiant stars. A comparison of the
ratio between the SMC and Galactic samples, while
consistent with the above statement, emphasizes that the uncertainties in the
distances to galactic O-stars are a serious obstacle to a detailed comparison
with theory. For the SMC sample there is considerable scatter in this ratio at
a given effective temperature, perhaps indicative of uncertainties in stellar
masses.Comment: 28 pages, 8 figures, accepted by ApJ; minor revisions prior to
acceptanc
Differential O and Si Abundances in M33 Early B Supergiants
We present non-LTE analyses of four M33 early B-supergiant stars and five
Galactic counterparts. This is the first time that B supergiants beyond the
Magellanic Clouds are analyzed by means of detailed Non-LTE techniques. Stellar
temperatures, gravities, microturbulences and Si abundances are derived for all
objects using the Si ionization equilibrium and the Balmer line wings. O
abundances are then also derived. Important approximations made during the
calculations are described, and their influence on the results is analyzed. It
is found that these approximations have no significant effect on the results at
any microturbulence. We find that a strict differential analysis is needed to
detect abundance differences. Thus we compare results line by line in M33 and
Galactic stars of stellar parameters as similar as possible. Three of the four
M33 stars turned out to be O deficient as compared to their Galactic
counterparts, and only one, close to the center of M33 (M33 1054) is found to
be moderately O enriched. From these differential analyses we find that our
data are compatible with a radial O gradient in M33 as that derived from HII
region data: we obtain -0.19+/-0.13 or -0.20+/-0.07 dex/kpc, depending on
whether B133 is included or not. Our data are also consistent with other
possibilities such as a steep increase of the O abundance in the inner region
(at projected distances less than 9 arcmin from the center of M33), followed by
a flat O abundance profile towards the outer parts of M33. Si shows the same
pattern, and it is shown that Si and O correlate well, as expected for
alpha-elements, supporting then the high value of the O abundance gradient in
M33 as compared to the Milky Way and other nearby spiral galaxies.Comment: Accepted for ApJ. Tentatively scheduled for Dec. 20, 2000. 44 pages,
9 tables, 18 figure
DNA Methylome Alterations are Associated with Airway Macrophage Differentiation and Phenotype During Lung Fibrosis
RATIONALE: Airway macrophages (AMs) are key regulators of the lung environment and are implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a fatal respiratory disease with no cure. However, knowledge of epigenetics of AMs in IPF are limited. METHODS: We undertook DNA methylation profiling using Illumina EPIC (850k) arrays in sorted AMs from Healthy (n=14) and IPF (n=30) donors. Cell-type deconvolution was performed using reference myeloid-cell DNA methylomes. MEASUREMENTS AND MAIN RESULTS: Our analysis revealed epigenetic heterogeneity was a key characteristic of IPF-AMs. DNAm 'clock' analysis indicated epigenetic alterations in IPF-AMs was not associated with accelerated ageing. In differential DNAm analysis, we identified numerous differentially methylated positions (DMPs, n=11) and regions (DMRs, n=49) between healthy and IPF AMs respectively. DMPs and DMRs encompassed genes involved in lipid (LPCAT1) and glucose (PFKFB3) metabolism and importantly, DNAm status was associated with disease severity in IPF. CONCLUSIONS: Collectively, our data identify that changes in the epigenome are associated with development and function of AMs in the IPF lung
A Be star with a low nitrogen abundance in the SMC cluster NGC330
High-resolution UVES/VLT spectra of B12, an extreme pole-on Be star in the
SMC cluster NGC330, have been analysed using non-LTE model atmospheres to
obtain its chemical composition relative to the SMC standard star AV304. We
find a general underabundance of metals which can be understood in terms of an
extra contribution to the stellar continuum due to emission from a disk which
we estimate to be at the ~25% level. When this is corrected for, the nitrogen
abundance for B12 shows no evidence of enhancement by rotational mixing as has
been found in other non-Be B-type stars in NGC330, and is inconsistent with
evolutionary models which include the effects of rotational mixing. A second Be
star, NGC330-B17, is also shown to have no detectable nitrogen lines. Possible
explanations for the lack of rotational mixing in these rapidly rotating stars
are discussed, one promising solution being the possibility that magnetic
fields might inhibit rotational mixing.Comment: 7 pages, 4 figures. Submitted to A&
The transferrin receptor CD71 delineates functionally distinct airway macrophage subsets during idiopathic pulmonary fibrosis
RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a devastating progressive disease with limited therapeutic options. Airway macrophages (AMs) are key components of the defence of the airways and are implicated in the pathogenesis of IPF. Alterations in iron metabolism have been described during fibrotic lung disease and in murine models of lung fibrosis. However, the role of transferrin receptor-1 (CD71)-expressing AMs in IPF is not known. OBJECTIVES: To assess the role of CD71 expressing AMs in the IPF-lung. METHODS: We utilized multi-parameter flow cytometry, gene expression analysis and phagocytosis/transferrin uptake assays to delineate the role of AMs expressing, or lacking, CD71 in the BAL of patients with IPF or healthy controls. MEASUREMENTS AND MAIN RESULTS: There was a distinct increase in proportions of AMs lacking CD71 in IPF patients in comparison to healthy controls. Levels of BAL transferrin were enhanced in IPF-BAL and furthermore, CD71- AMs had an impaired ability to sequester transferrin. CD71+ and CD71- AMs were phenotypically, functionally and transcriptionally distinct, with CD71- AMs characterised by reduced expression of markers of macrophage maturity, impaired phagocytosis and enhanced expression of pro-fibrotic genes. Importantly, proportions of AMs lacking CD71 were independently associated with worse survival, underlining the importance of this population in IPF and as a potential therapeutic target. CONCLUSIONS: Taken together these data highlight how CD71 delineates AM subsets which play distinct roles in IPF and furthermore, CD71- AMs may be an important pathogenic component of fibrotic lung disease
Genetics, recombination and clinical features of human rhinovirus species C (HRV-C) infections; interactions of HRV-C with other respiratory viruses
To estimate the frequency, molecular epidemiological and clinical associations of infection with the newly described species C variants of human rhinoviruses (HRV), 3243 diagnostic respiratory samples referred for diagnostic testing in Edinburgh were screened using a VP4-encoding region-based selective polymerase chain reaction (PCR) for HRV-C along with parallel PCR testing for 13 other respiratory viruses. HRV-C was the third most frequently detected behind respiratory syncytial virus (RSV) and adenovirus, with 141 infection episodes detected among 1885 subjects over 13 months (7.5%). Infections predominantly targeted the very young (median age 6–12 months; 80% of infections in those <2 years), occurred throughout the year but with peak incidence in early winter months. HRV-C was detected significantly more frequently among subjects with lower (LRT) and upper respiratory tract (URT) disease than controls without respiratory symptoms; HRV-C mono-infections were the second most frequently detected virus (behind RSV) in both disease presentations (6.9% and 7.8% of all cases respectively). HRV variants were classified by VP4/VP2 sequencing into 39 genotypically defined types, increasing the current total worldwide to 60. Through sequence comparisons of the 5′untranslated region (5′UTR), the majority grouped with species A (n = 96; 68%, described as HRV-Ca), the remainder forming a phylogenetically distinct 5′UTR group (HRV-Cc). Multiple and bidirectional recombination events between HRV-Ca and HRV-Cc variants and with HRV species A represents the most parsimonious explanation for their interspersed phylogeny relationships in the VP4/VP2-encoding region. No difference in age distribution, seasonality or disease associations was identified between HRV-Ca and HRV-Cc variants. HRV-C-infected subjects showed markedly reduced detection frequencies of RSV and other respiratory viruses, providing evidence for a major interfering effect of HRV-C on susceptibility to other respiratory virus infections. HRV-C's disease associations, its prevalence and evidence for interfering effects on other respiratory viruses mandates incorporation of rhinoviruses into future diagnostic virology screening
A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti
The massive interacting binary RY Scuti is an important representative of an
active mass-transferring system that is changing before our eyes and which may
be an example of the formation of a Wolf-Rayet star through tidal stripping.
Utilizing new and previously published spectra, we present examples of how a
number of illustrative absorption and emission features vary during the binary
orbit. We identify spectral features associated with each component, calculate
a new, double-lined spectroscopic binary orbit, and find masses of 7.1 +/- 1.2
M_sun for the bright supergiant and 30.0 +/- 2.1 M_sun for the hidden massive
companion. Through tomographic reconstruction of the component spectra from the
composite spectra, we confirm the O9.7 Ibpe spectral class of the bright
supergiant and discover a B0.5 I spectrum associated with the hidden massive
companion; however, we suggest that the latter is actually the spectrum of the
photosphere of the accretion torus immediately surrounding the massive
companion. We describe the complex nature of the mass loss flows from the
system in the context of recent hydrodynamical models for beta Lyr, leading us
to conclude RY Scuti has matter leaving the system in two ways: 1) a bipolar
outflow from winds generated by the hidden massive companion, and 2) mass from
the bright O9.7 Ibpe supergiant flowing from the region near the L2 point to
fill out a large, dense circumbinary disk. This circumbinary disk (radius ~ 1
AU) may feed the surrounding double-toroidal nebula (radius ~ 2000 AU).Comment: 41 pages with 7 tables and 11 figures, accepted to Ap
Modelling the clumping-induced polarimetric variability of hot star winds
Clumping in the winds of massive stars may significantly reduce empirical
mass-loss rates, and which in turn may have a large impact on our understanding
of massive star evolution. Here, we investigate wind-clumping through the
linear polarization induced by light scattering off the clumps. Through the use
of an analytic wind clumping model, we predict the time evolution of the linear
polarimetry over a large parameter space. We concentrate on the Luminous Blue
Variables, which display the greatest amount of polarimetric variability and
for which we recently conducted a spectropolarimetric survey. Our model results
indicate that the observed level of polarimetric variability can be reproduced
for two regimes of parameter space: one of a small number of massive,
optically-thick clumps; and one of a very large number of low-mass clumps.
Although a systematic time-resolved monitoring campaign is required to
distinguish between the two scenarios, we currently favour the latter, given
the short timescale of the observed polarization variability. As the
polarization is predicted to scale linearly with mass-loss rate, we anticipate
that all hot stars with very large mass-loss rates should display polarimetric
variability. This is consistent with recent findings that intrinsic
polarization is more common in stars with strong H emission.Comment: 12 pages, 11 figures, accepted to A&
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